/* This file manages the inode table.  There are procedures to allocate and
 * deallocate inodes, acquire, erase, and release them, and read and write
 * them from the disk.
 *
 * The entry points into this file are
 *   get_inode:	   search inode table for a given inode; if not there,
 *                 read it
 *   put_inode:	   indicate that an inode is no longer needed in memory
 *   alloc_inode:  allocate a new, unused inode
 *   wipe_inode:   erase some fields of a newly allocated inode
 *   free_inode:   mark an inode as available for a new file
 *   update_times: update atime, ctime, and mtime
 *   rw_inode:	   read a disk block and extract an inode, or corresp. write
 *   old_icopy:	   copy to/from in-core inode struct and disk inode (V1.x)
 *   new_icopy:	   copy to/from in-core inode struct and disk inode (V2.x)
 *   dup_inode:	   indicate that someone else is using an inode table entry
 */

#include "fs.h"
#include "buf.h"
#include "file.h"
#include "fproc.h"
#include "inode.h"
#include "super.h"

FORWARD _PROTOTYPE( void old_icopy, (struct inode *rip, d1_inode *dip,
	    int direction, int norm));
FORWARD _PROTOTYPE( void new_icopy, (struct inode *rip, d2_inode *dip,
	    int direction, int norm));

/*===========================================================================*
 *				get_inode				     *
 *===========================================================================*/
PUBLIC struct inode *get_inode(dev, numb)
    dev_t dev;			/* device on which inode resides */
    int numb;			/* inode number (ANSI: may not be unshort) */
{
    /* Find a slot in the inode table, load the specified inode into it, and
     * return a pointer to the slot.  If 'dev' == NO_DEV, just return a free slot.
     */

    register struct inode *rip, *xp;

    /* Search the inode table both for (dev, numb) and a free slot. */
    xp = NIL_INODE;
    for (rip = &inode[0]; rip < &inode[NR_INODES]; rip++) {
	if (rip->i_count > 0) { /* only check used slots for (dev, numb) */
	    if (rip->i_dev == dev && rip->i_num == numb) {
		/* This is the inode that we are looking for. */
		rip->i_count++;
		return(rip);	/* (dev, numb) found */
	    }
	} else {
	    xp = rip;	/* remember this free slot for later */
	}
    }

    /* Inode we want is not currently in use.  Did we find a free slot? */
    if (xp == NIL_INODE) {	/* inode table completely full */
	err_code = ENFILE;
	return(NIL_INODE);
    }

    /* A free inode slot has been located.  Load the inode into it. */
    xp->i_dev = dev;
    xp->i_num = numb;
    xp->i_count = 1;
    if (dev != NO_DEV) rw_inode(xp, READING);	/* get inode from disk */
    xp->i_update = 0;		/* all the times are initially up-to-date */

    return(xp);
}

/*===========================================================================*
 *				put_inode				     *
 *===========================================================================*/
PUBLIC void put_inode(rip)
    register struct inode *rip;	/* pointer to inode to be released */
{
    /* The caller is no longer using this inode.  If no one else is using it either
     * write it back to the disk immediately.  If it has no links, truncate it and
     * return it to the pool of available inodes.
     */

    if (rip == NIL_INODE) return;	/* checking here is easier than in caller */
    if (--rip->i_count == 0) {	/* i_count == 0 means no one is using it now */
	if (rip->i_nlinks == 0) {
	    /* i_nlinks == 0 means free the inode. */
	    truncate(rip);	/* return all the disk blocks */
	    rip->i_mode = I_NOT_ALLOC;	/* clear I_TYPE field */
	    rip->i_dirt = DIRTY;
	    free_inode(rip->i_dev, rip->i_num);
	} else {
	    if (rip->i_pipe == I_PIPE) truncate(rip);
	}
	rip->i_pipe = NO_PIPE;  /* should always be cleared */
	if (rip->i_dirt == DIRTY) rw_inode(rip, WRITING);
    }
}

/*===========================================================================*
 *				alloc_inode				     *
 *===========================================================================*/
PUBLIC struct inode *alloc_inode(dev_t dev, mode_t bits)
{
    /* Allocate a free inode on 'dev', and return a pointer to it. */

    register struct inode *rip;
    register struct super_block *sp;
    int major, minor, inumb;
    bit_t b;

    sp = get_super(dev);	/* get pointer to super_block */
    if (sp->s_rd_only) {	/* can't allocate an inode on a read only device. */
	err_code = EROFS;
	return(NIL_INODE);
    }

    /* Acquire an inode from the bit map. */
    b = alloc_bit(sp, IMAP, sp->s_isearch);
    if (b == NO_BIT) {
	err_code = ENFILE;
	major = (int) (sp->s_dev >> MAJOR) & BYTE;
	minor = (int) (sp->s_dev >> MINOR) & BYTE;
	printf("Out of i-nodes on %sdevice %d/%d\n",
		sp->s_dev == root_dev ? "root " : "", major, minor);
	return(NIL_INODE);
    }
    sp->s_isearch = b;		/* next time start here */
    inumb = (int) b;		/* be careful not to pass unshort as param */

    /* Try to acquire a slot in the inode table. */
    if ((rip = get_inode(NO_DEV, inumb)) == NIL_INODE) {
	/* No inode table slots available.  Free the inode just allocated. */
	free_bit(sp, IMAP, b);
    } else {
	/* An inode slot is available. Put the inode just allocated into it. */
	rip->i_mode = bits;		/* set up RWX bits */
	rip->i_nlinks = 0;		/* initial no links */
	rip->i_uid = fp->fp_effuid;	/* file's uid is owner's */
	rip->i_gid = fp->fp_effgid;	/* ditto group id */
	rip->i_dev = dev;		/* mark which device it is on */
	rip->i_ndzones = sp->s_ndzones;	/* number of direct zones */
	rip->i_nindirs = sp->s_nindirs;	/* number of indirect zones per blk*/
	rip->i_sp = sp;			/* pointer to super block */

	/* Fields not cleared already are cleared in wipe_inode().  They have
	 * been put there because truncate() needs to clear the same fields if
	 * the file happens to be open while being truncated.  It saves space
	 * not to repeat the code twice.
	 */
	wipe_inode(rip);
    }

    return(rip);
}

/*===========================================================================*
 *				wipe_inode				     *
 *===========================================================================*/
PUBLIC void wipe_inode(rip)
    register struct inode *rip;	/* the inode to be erased */
{
    /* Erase some fields in the inode.  This function is called from alloc_inode()
     * when a new inode is to be allocated, and from truncate(), when an existing
     * inode is to be truncated.
     */

    register int i;

    rip->i_size = 0;
    rip->i_update = ATIME | CTIME | MTIME;	/* update all times later */
    rip->i_dirt = DIRTY;
    for (i = 0; i < V2_NR_TZONES; i++) rip->i_zone[i] = NO_ZONE;
}

/*===========================================================================*
 *				free_inode				     *
 *===========================================================================*/
PUBLIC void free_inode(dev, inumb)
    dev_t dev;			/* on which device is the inode */
    ino_t inumb;			/* number of inode to be freed */
{
    /* Return an inode to the pool of unallocated inodes. */

    register struct super_block *sp;
    bit_t b;

    /* Locate the appropriate super_block. */
    sp = get_super(dev);
    if (inumb <= 0 || inumb > sp->s_ninodes) return;
    b = inumb;
    free_bit(sp, IMAP, b);
    if (b < sp->s_isearch) sp->s_isearch = b;
}

/*===========================================================================*
 *				update_times				     *
 *===========================================================================*/
PUBLIC void update_times(rip)
    register struct inode *rip;	/* pointer to inode to be read/written */
{
    /* Various system calls are required by the standard to update atime, ctime,
     * or mtime.  Since updating a time requires sending a message to the clock
     * task--an expensive business--the times are marked for update by setting
     * bits in i_update.  When a stat, fstat, or sync is done, or an inode is 
     * released, update_times() may be called to actually fill in the times.
     */

    time_t cur_time;
    struct super_block *sp;

    sp = rip->i_sp;		/* get pointer to super block. */
    if (sp->s_rd_only) return;	/* no updates for read-only file systems */

    cur_time = clock_time();
    if (rip->i_update & ATIME) rip->i_atime = cur_time;
    if (rip->i_update & CTIME) rip->i_ctime = cur_time;
    if (rip->i_update & MTIME) rip->i_mtime = cur_time;
    rip->i_update = 0;		/* they are all up-to-date now */
}

/*===========================================================================*
 *				rw_inode				     *
 *===========================================================================*/
PUBLIC void rw_inode(rip, rw_flag)
    register struct inode *rip;	/* pointer to inode to be read/written */
    int rw_flag;			/* READING or WRITING */
{
    /* An entry in the inode table is to be copied to or from the disk. */

    register struct buf *bp;
    register struct super_block *sp;
    d1_inode *dip;
    d2_inode *dip2;
    block_t b, offset;

    /* Get the block where the inode resides. */
    sp = get_super(rip->i_dev);	/* get pointer to super block */
    rip->i_sp = sp;		/* inode must contain super block pointer */
    offset = sp->s_imap_blocks + sp->s_zmap_blocks + 2;
    b = (block_t) (rip->i_num - 1)/sp->s_inodes_per_block + offset;
    bp = get_block(rip->i_dev, b, NORMAL);
    dip  = bp->b_v1_ino + (rip->i_num - 1) % V1_INODES_PER_BLOCK;
    dip2 = bp->b_v2_ino + (rip->i_num - 1) %
	V2_INODES_PER_BLOCK(sp->s_block_size);

    /* Do the read or write. */
    if (rw_flag == WRITING) {
	if (rip->i_update) update_times(rip);	/* times need updating */
	if (sp->s_rd_only == FALSE) bp->b_dirt = DIRTY;
    }

    /* Copy the inode from the disk block to the in-core table or vice versa.
     * If the fourth parameter below is FALSE, the bytes are swapped.
     */
    if (sp->s_version == V1)
	old_icopy(rip, dip,  rw_flag, sp->s_native);
    else
	new_icopy(rip, dip2, rw_flag, sp->s_native);

    put_block(bp, INODE_BLOCK);
    rip->i_dirt = CLEAN;
}

/*===========================================================================*
 *				old_icopy				     *
 *===========================================================================*/
PRIVATE void old_icopy(rip, dip, direction, norm)
    register struct inode *rip;	/* pointer to the in-core inode struct */
    register d1_inode *dip;		/* pointer to the d1_inode inode struct */
    int direction;			/* READING (from disk) or WRITING (to disk) */
    int norm;			/* TRUE = do not swap bytes; FALSE = swap */

{
    /* The V1.x IBM disk, the V1.x 68000 disk, and the V2 disk (same for IBM and
     * 68000) all have different inode layouts.  When an inode is read or written
     * this routine handles the conversions so that the information in the inode
     * table is independent of the disk structure from which the inode came.
     * The old_icopy routine copies to and from V1 disks.
     */

    int i;

    if (direction == READING) {
	/* Copy V1.x inode to the in-core table, swapping bytes if need be. */
	rip->i_mode    = conv2(norm, (int) dip->d1_mode);
	rip->i_uid     = conv2(norm, (int) dip->d1_uid );
	rip->i_size    = conv4(norm,       dip->d1_size);
	rip->i_mtime   = conv4(norm,       dip->d1_mtime);
	rip->i_atime   = rip->i_mtime;
	rip->i_ctime   = rip->i_mtime;
	rip->i_nlinks  = dip->d1_nlinks;		/* 1 char */
	rip->i_gid     = dip->d1_gid;			/* 1 char */
	rip->i_ndzones = V1_NR_DZONES;
	rip->i_nindirs = V1_INDIRECTS;
	for (i = 0; i < V1_NR_TZONES; i++)
	    rip->i_zone[i] = conv2(norm, (int) dip->d1_zone[i]);
    } else {
	/* Copying V1.x inode to disk from the in-core table. */
	dip->d1_mode   = conv2(norm, (int) rip->i_mode);
	dip->d1_uid    = conv2(norm, (int) rip->i_uid );
	dip->d1_size   = conv4(norm,       rip->i_size);
	dip->d1_mtime  = conv4(norm,       rip->i_mtime);
	dip->d1_nlinks = rip->i_nlinks;			/* 1 char */
	dip->d1_gid    = rip->i_gid;			/* 1 char */
	for (i = 0; i < V1_NR_TZONES; i++)
	    dip->d1_zone[i] = conv2(norm, (int) rip->i_zone[i]);
    }
}

/*===========================================================================*
 *				new_icopy				     *
 *===========================================================================*/
PRIVATE void new_icopy(rip, dip, direction, norm)
    register struct inode *rip;	/* pointer to the in-core inode struct */
    register d2_inode *dip;	/* pointer to the d2_inode struct */
    int direction;			/* READING (from disk) or WRITING (to disk) */
    int norm;			/* TRUE = do not swap bytes; FALSE = swap */

{
    /* Same as old_icopy, but to/from V2 disk layout. */

    int i;

    if (direction == READING) {
	/* Copy V2.x inode to the in-core table, swapping bytes if need be. */
	rip->i_mode    = conv2(norm,dip->d2_mode);
	rip->i_uid     = conv2(norm,dip->d2_uid);
	rip->i_nlinks  = conv2(norm,dip->d2_nlinks);
	rip->i_gid     = conv2(norm,dip->d2_gid);
	rip->i_size    = conv4(norm,dip->d2_size);
	rip->i_atime   = conv4(norm,dip->d2_atime);
	rip->i_ctime   = conv4(norm,dip->d2_ctime);
	rip->i_mtime   = conv4(norm,dip->d2_mtime);
	rip->i_ndzones = V2_NR_DZONES;
	rip->i_nindirs = V2_INDIRECTS(rip->i_sp->s_block_size);
	for (i = 0; i < V2_NR_TZONES; i++)
	    rip->i_zone[i] = conv4(norm, (long) dip->d2_zone[i]);
    } else {
	/* Copying V2.x inode to disk from the in-core table. */
	dip->d2_mode   = conv2(norm,rip->i_mode);
	dip->d2_uid    = conv2(norm,rip->i_uid);
	dip->d2_nlinks = conv2(norm,rip->i_nlinks);
	dip->d2_gid    = conv2(norm,rip->i_gid);
	dip->d2_size   = conv4(norm,rip->i_size);
	dip->d2_atime  = conv4(norm,rip->i_atime);
	dip->d2_ctime  = conv4(norm,rip->i_ctime);
	dip->d2_mtime  = conv4(norm,rip->i_mtime);
	for (i = 0; i < V2_NR_TZONES; i++)
	    dip->d2_zone[i] = conv4(norm, (long) rip->i_zone[i]);
    }
}

/*===========================================================================*
 *				dup_inode				     *
 *===========================================================================*/
PUBLIC void dup_inode(ip)
    struct inode *ip;		/* The inode to be duplicated. */
{
    /* This routine is a simplified form of get_inode() for the case where
     * the inode pointer is already known.
     */

    ip->i_count++;
}
